Ground Anchors & Nailing

  •  Re-assessing a soil nailing design in heavily weathered granite after a strong earthquake

    Abstract: Soil nailing is increasingly adopted in potentially unstable slopes and steep excavations in Concepcio´n, Chile. The paper presents a study of soil nailing design and construction in Maicillo, a heavily weathered granite. The stability of the soil nailed wall was analysed using a limit equilibrium block method. The lowest factor of safety was obtained when the nailed wall was 8 m high but without the bottom row of nails. This was followed by the global seismic case using an acceleration factor kh = 0.15. The occurrence of a strong earthquake (magnitude 8.8) 2 weeks after completion of the projected allowed a re-assessment of the soil nailing design. Despite registering a maximum acceleration of 0.63 g near the project site, the nailed wall did not present any damage, probably due to the use of undrained shear strength parameters.

  •  2D numerical simulations of soil nail walls

    Abstract: In practice, numerical simulations of soil nail walls are often carried out to assess the performance and stability. In the present study, implications of the use of advanced soil models, such as hardening soil model and hardening soil with small-strain stiffness model to simulate the behavior of in situ soil on the overall response of simulated soil nail wall have been studied, and compared with respect to the analysis using conventional and most prevalently used Mohr-Coulomb soil model. Further, influence of the consideration of bending stiffness of soil nails on the simulation results has been examined. Results of the simulations indicated that the use of advanced models is desirable for cases of soil nail walls constructed in soft soils and when lateral wall displacements are critical to the adjoining structures. Incorporation of bending stiffness of nails is found important from the consideration of facing failure modes of soil nail walls.

  •  Numerical analysis of performance of soil nail walls in seismic conditions

    Abstract: Evidences from the field and full-scale laboratory tests suggest that soil nail walls perform remarkably well under seismic conditions. In this study an attempt has been made to study the performance of a soil nail wall supporting a vertical cut of 8 m height under seismic conditions. The wall is designed in conventional manner by using the allowable stress design procedure. The response of the wall is then simulated numerically by using a finite element analysis. Seismic data from Bhuj and Uttarkashi earthquakes is used for the pseudo-static and dynamic analyses. To assess the performance of the soil nail wall, parameters such as maximum lateral displacements, development of nail forces, important failure modes of soil nail walls, have been studied under both static and seismic conditions. Results of the numerical analyses indicate that the use of soil nail walls is desirable to impart stability to the retaining systems under seismic conditions.

  •  Numerical simulation of ground anchors

    Abstract: A procedure of finite-element modeling and beam-column modeling of ground anchors was proposed in this study to investigate the load transfer mechanism in ground anchors. The procedure included the modeling of soil, grout, and strand tendon and the interface modeling of soil–grout and grout–strand in ground anchors. A series of finite element analyses and beam-column analyses were performed using the proposed models on ground anchors. The numerical predictions were compared with observed measurements in a field load test. The results indicated that the numerical simulation of load transfer mechanism on ground anchors can provide reasonable predictions.

  •  Advancements in ground anchors: Carbon Fibre Reinforced Polymer (CFRP) strands

    Abstract: Steel tendon ground anchors are an integral construction technique for numerous civil engineering applications ranging from deep excavation support to resistance of structural uplift and overturning of superstructures. Corrosion and human error generally causes failure of steel tendon ground anchors. Several methods of minimising anchor system corrosion have been adopted over time to minimise ingress of corrosive substances. Anchors are still failing due to corrosion. Advancement in the development of corrosion resistant materials has been at the forefront of materials research. Research and development of FRP materials has enabled the progress of providing the industry with a more potentially robust anchor system aimed at eliminating current limitations encountered with steel strand ground anchors. This paper investigates current developments in FRP materials for ground anchor applications as an alternative to conventional steel tendon ground anchors.